There are ways to adjust to a change in elevation. Try to get to the site of the race or climb a week ahead of time to acclimatize. If that isn't an option, endurance training at sea level can make it easier to acclimatize.

Ecuadorean mountaineer and Lonely Summits guide Edgar Parra carefully packs up his waterproof duffel bag and 70-liter backpack for climbing peaks in the Andes in Ecuador, Peru, Bolivia and Argentina. His list includes layers for warmth, ropes, cooking tools and enough Snickers bars to eat three a day.

Ecuadorean mountaineer and Lonely Summits guide Edgar Parra brings 104 essential items up the world’s largest mountains in a waterproof duffel bag and a 70-liter backpack. He packs ropes, a helmet, an iPod and cooking gear.